The pioneering years in the history of capacitors were when capacitors were mainly used for early understanding of electricity, even before the discovery of electrons. This is also the time for living room demonstrations, such as having a row of people holding hands and discharging capacitors through them. The modern era of capacitors began in the late 1800s. With the advent of the practical application of electricity, reliable capacitors with specific characteristics are required.

Marconi with launcher, published on LIFE [Public Domain] via Wikimedia CommonsOne, this practical use was Marconi’s wireless spark gap launcher that started before 1900 and entered the first and second decades middle. The transmitter builds a high voltage to discharge through the spark gap, so ceramic capacitors are used to withstand this voltage. High frequency is also needed. These are basically Leiden tanks and a lot of space is needed to obtain the required capacitance.

In 1909, William Dubilier invented a smaller mica capacitor, which was then used in a resonant circuit in wireless hardware at the receiving end.

Early mica capacitors basically sandwiched the mica layer and copper foil together, called "clamp-on mica capacitors". However, these capacitors are not very reliable. Only the mica sheet is pressed on the metal foil, and there is an air gap between the mica and the foil. These gaps allow oxidation and corrosion, which means that the distance between the plates will change, thereby changing the capacitance.

In the 1920s, silver mica capacitors were developed, in which both sides of the mica were coated with metal to eliminate air gaps. By replacing thicker foils with thin metal coatings, capacitors can also be made smaller. These are very reliable. Of course, we did not stop there. The modern era of capacitors is marked by fascinating stories, one breakthrough after another. let's see.

MLCC around the microprocessor. Author: Elcap [CC BY-SA 3.0], from Wikimedia Commons In the 1920s, mica was not abundant in Germany, so they tried a new series of ceramic capacitors and found that titanium dioxide (rutile) has a linear temperature-dependent compensation for the temperature of the capacitor , Can replace mica capacitors. They were initially produced in small batches, and mass production began in the 1940s. They consist of metalized discs on both sides.

In order to obtain higher capacitance, another ceramic uses barium titanate because its dielectric constant is 10 times that of mica or titanium dioxide. However, their electrical parameters are not stable and can only replace mica where stability is not important. This was improved after World War II.

The American company established in 1961 took the lead in introducing multilayer ceramic capacitors (MLCC) with a smaller volume and a higher capacity. As of 2012, more than 10^12 barium titanate MLCCs have been produced every year.

In the 1890s, Charles Pollak discovered that the oxide layer on the aluminum anode was stable in neutral or alkaline solutions, and in 1897 obtained a patent for borax electrolytic aluminum capacitors. The first "wet" electrolytic capacitor appeared in radios briefly in the 1920s, but had a limited lifespan. Because of their high water content, they are called "wet". They are basically a container where the metal anode is immersed in borax or other electrolyte solution dissolved in water. The outside of the container serves as another plate. These are used in large telephone exchanges to reduce relay noise.

Samual Ruben filed a patent for the modern ancestor of electrolytic capacitors in 1925. He sandwiched a gel-like electrolyte between the oxide-coated anode and the second metal foil, eliminating the need for a water container. The result is a "dry" electrolytic capacitor. Another addition is the paper space between the turns of the foil. All of these have significantly reduced the size and price.

In 1936, the Cornell-Dubilier company introduced their aluminum electrolytic capacitors, which included improvements such as roughening the anode surface to increase capacitance. AEG's Hydra-Werke also started mass production in Berlin, Germany.

After the Second World War, the rapid development of radio and television technology led to an increase in the number of production and the diversification of styles and sizes. Improvements include the use of new organic-based electrolytes to reduce leakage current and equivalent series resistance (ESR), a wider temperature range and longer life. Further developments from the 1970s to the 1990s included reducing leakage current, further reducing ESR, and increasing temperature.

The well-known "capacitor plague" occurred between 2000 and 2005, probably due to the use of stolen formulas but the lack of certain stable substances leading to premature failure.

A surface mount tantalum capacitor. Through Epop [Public Domain], through Wikimedia Commons Tantalum electrolytic capacitors were first manufactured for military purposes in the 1930s. These use wound tantalum foil and non-solid electrolyte. In the 1950s, Bell Laboratories manufactured the first solid electrolytic tantalum capacitor. They grind tantalum into powder and then sinter it into a cylinder. At first they used a liquid electrolyte, but then they discovered that manganese dioxide can be used as a solid electrolyte.

Although Bell Labs made a fundamental invention, in 1954, Sprague Electric Company improved the process and produced the first commercially viable tantalum solid electrolytic capacitor.

In 1975, polymer tantalum electrolytic capacitors appeared. The capacitors had a higher conductivity of conductive polymers instead of manganese dioxide, which resulted in lower ESR. NEC released polymer tantalum capacitors for SMD (Surface Mount Device) in 1995, and Sanyo followed suit in 1997.

Tantalum ore is vulnerable to price shocks. Two such incidents occurred in 1980 and 2000/2001. The latter's impact led to the development of niobium electrolytic capacitors, which use manganese dioxide electrolyte to provide roughly the same characteristics as tantalum capacitors.

Film capacitors. Elcap [CC-BY-SA 3.0], from Wikimedia Commons Metallized paper capacitors were patented by GF Mansbridge in 1900. Metallization is accomplished by coating paper with a binder filled with metal particles. These were commonly used as decoupling capacitors in telephones (telecommunications) in the early 1900s. During World War II, Bosch improved the process and manufactured them by painting paper and coating with vacuum deposited metal. Around 1954, Bell Laboratories produced a 2.5-micron thick metal paint film and separated it from the paper to obtain a smaller capacitor. This can be considered the first polymer film capacitor.

Organic chemists' research on plastics during World War II took this process a step further. In 1954, the first polyester film capacitor was one of them. Mylar was registered as a trademark by Dupont in 1952 and is a very strong PET (polyethylene terephthalate). In 1954, a 12um metalized polyester film capacitor was produced. By 1959, the list included capacitors made of polyethylene, polystyrene, polytetrafluoroethylene, PET, and polycarbonate. By 1970, power companies began to use film capacitors without paper.

Supercapacitors, Maxwell Technologies, Inc. [CC BY-SA 3.0], from Wikimedia Commons This brings us to the last type of capacitor, and a rather exciting type of capacitor with a capacitance of thousands of farads. In the early 1950s, researchers at General Electric used their background in fuel cells and rechargeable batteries to test capacitors with porous carbon electrodes. This led H. Becker to apply for a patent for the capacitor as a "low-voltage electrolytic capacitor with porous carbon electrode", but did not understand the principle behind it, resulting in extremely high capacity. GE did not pursue this further.

Ohio Standard Oil developed another version and finally licensed it to NEC in the 1970s, which eventually commercialized it under the brand name Super Capacitor. It has a rated voltage of 5.5V and a capacitance of up to 1F. They have a maximum size of 5 cm^3 and are used as a backup power source for computer memory.

Brian Evans Conway, professor emeritus of the University of Ottawa, was engaged in the research of ruthenium oxide electrochemical capacitors from 1975 to 1980. In 1991, he described the difference between supercapacitors and batteries in electrochemical storage, and in 1999 gave a complete explanation, and at the same time coined the term supercapacitor again.

Product and market growth is slow. Product names include Goldcaps, Dynacap and PRI Ultracapacitor. The latter is the first low internal resistance supercapacitor developed by Pinnacle Research Institute (PRI) in 1982 for military purposes.

Recent developments on the market include lithium ion capacitors with lithium ion doped activated carbon anodes. They have a capacitance of several thousand farads (4 bits) around 2.7V.

Based on your comment on our Capacitor History-Pioneer Year post, the use of the term capacitor does not lack capacitors rather than capacitors. So where did the word capacitor come from? This seems unknown, but the Oxford English Dictionary quotes the 1922 BSI (British Standards Institute?) Electrical Engineering Glossary, which says "capacitor" is a "new term" and it is recommended to avoid confusion with steam "condenser" .

Although our capacitor history ends here, but based on the large number of types of capacitors, we are sure that more can be added. If you have any interesting supplementary suggestions, please let us know below. History is only part of the path of progress, let us know any current or anticipated future developments you know. What do Hackaday writers 50 years later think about capacitors today and in the next 50 years?

Hello, I have read this article and left a simple question. The beginning of the article is about alu. eleco's "These are used in large telephone exchanges to reduce relay noise.". So now my question is why? How does this work? Do they stack them around the relay to form some kind of sound barrier? I'm sure it is not, but how do you mute the relay with capacitor. I do know a way to reduce the current consumption of the relay circuit, just connect a resistor in series with the relay and place a large capacitor on the resistor. In this way, the relay has the ability to properly attract (using the load current of the capacitor). When the capacitor is full, the resistor takes over and limits the holding current of the relay. But silence? Does anyone know any details?

I think they reduce electrical noise, not acoustic noise.

Haha, I didn't expect it, haha. Stupid me. I was very focused on thinking about the audible noise of the continuous switching of hundreds of relays, and I never even realized that they could mean electrical noise.

It is likely to cause noise at both ends of the phone line....

Don't forget wax paper capacitors. They are made of multiple layers of conductive foil and wax paper, rolled up. They can be found in many electronic products before the 1970s, where we now use polyester film or ceramic capacitors. They are so large that they become leaky when they absorb moisture from the air.

When I was growing up, this was what I took out of my old radio.

You will rarely see the word "adsorption" in the wild.

Beginners think it seems very common to specify polarized capacitors because they see them in the schematic. But I can't think of anything that requires polarized capacitors. The designation is a large-capacity capacitor, and the only way to obtain it, or at least in a reasonable size, is to use a polarized electrolyte.

What has changed is that bulk capacitors are now more common. In the age of electronic tubes, they may be filter capacitors in power supplies, audio couplings, and cathode bypasses in audio stages. And their values ​​are relatively small. Electron tubes are high voltages with high impedance and low current, so large-capacity capacitors are not sufficient. It is relatively easy to find a bad electrolyte. The buzzing sound in the audio means that the filter capacitor in the power supply is broken, and the low audio gain may mean that the cathode bypass capacitor is broken.

This changes as the transistor changes. Low voltage but higher current, they are low impedance and must have a larger value to be effective capacitors. Even the early transistor pocket radios have more electrolyte than the equivalent tube radios. If the bypass capacitor on the mains voltage is broken, you may see a motor boat.

This does mean that the electrolyte becomes better and smaller. I have one that is about the size of a Coke can. I bought it in 1973. It is 15000uF and the voltage is about 15V. Recently, you can get it in a smaller package.

Then it got worse. The advent of switching power supplies means that the value of the electrolyte does not have to be that great, because their operating frequency is much higher than the 60 Hz in the power supply. Computers and other digital devices have a lot of electrolytes, and they are located in crossed lines that may be seen. A lot of high-frequency noise. All this has had more impact on electrolysis, which did not exist a few decades ago. The circuit is more complicated, and bad capacitors may not be as obvious as in tube radios decades ago.

There is another series of capacitors not mentioned: varactor diodes. These devices are reverse-biased diodes, and their capacitance changes with the applied reverse-bias voltage. They often appear in voltage controlled oscillators, especially in older radio and television front ends. You can buy a real "varicap diode" that has reliable device characteristics, or you can try almost any diode-even LEDs. The junction capacitance of any diode will vary with the applied reverse bias voltage.

I think I would classify them as semiconductors instead of capacitors.

But yes, many semiconductor junctions provide this effect to varying degrees. Although an article a few decades ago warned about the use of ordinary diodes with transparent casings. His VCO buzzed until he realized that the transparent diode acting as a varactor was being modulated by the desk lamp.

Even when Sam Harris described the first practical parametric amplifier in CQ around 1958, he suggested to try other things first to get a feel for it, and then buy the new expensive varactor diodes at the time.

Varactor diode; but not true. 'Urban Legend', kind of. It really works. real.

A friend called to ask me if there is any small value (10pf-30pf) high frequency cap. It seems that he needs two CMOS clock oscillators that are ubiquitous in almost every microprocessor/controller, and usually uses capacitors in this range (HIS design requires capacitors of 15 pf and 22 pf. Of course). In order to solve the problem quickly, I suggest that he use two reverse-biased high-frequency signal diodes (1N4148, maybe? 1N914?) instead of capacitors, because their capacitance may be within the range he needs, and under the voltage he needs is using. It works; it works. (Note: low frequency rectifier diodes-such as 1N400X-will most likely not work; it will only act as a mushy bump. Sorry for all the high-tech talk)

"Sorry for all the high-tech talk" BAH! Hahaha!

Note to editors: You urgently need to gain a higher level of readers, otherwise you will face the same danger as Yahoo!’s "answer". You need to please readers who really know something, including the use of language.

Interesting reading.​​​ It would be nice to get something about variable capacitors there. As far as I know, they are very important in the early days of radio transmission. And, perhaps a bit too far off the topic, all applications where capacitors are actually used as direct sensor elements will also be interesting. It may be industrial sensors for process control, or capacitive touch buttons and touch screens...

I support the omission of variable capacitors. I suspect that an article is being produced. :)

I remembered again that I missed the time to sell 1500 Farah supercapacitors for $6 from online surplus.

Ouch. They are only 500F, I don't know how good they are, but a quick search on eBay found some very cheap (less than $6, free shipping) 500F, 2.7V supercapacitors. This is a 4.76 USD http://www.ebay.com/itm/1pcs-2-7V-500F-Super-Farad-Capacitor-Super-Capacitor-35-60mm-/182190031303?hash=item2a6b5f41c7:guz:5RXdSAOS4Iw

very good. I never know when the various types of capacitors will be put into use.

Hi, back to the January 2016 comments. Question how to use capacitors to eliminate relay noise. I suspect that a capacitor is placed between the switch contacts to eliminate arcing or transients when the contacts are opened and closed by the relay coil. The purpose of the contact is to switch the connection between the telephone lines. Capacitors can reduce clicks and clicks on the telephone line.

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